86 The Ottawa Naturalist. [July 



a year to build, and many months were occupied in testing and 

 making preliminary trials." Success attended the experiment 

 made on May loth when hydrogen gas at a temperature of -205 

 degrees C. and under a pressure of 180 atmospheres "was allowed 

 to continuously escape from the nozzle of a coil of pipe at the 

 rate of 10 to 15 cubic feet per minute, in a vacuum vessel doubly 

 silvered and of special construction, surrounded with a space 

 kept below -200 degrees C." Under these conditions liquid 

 hydrogen began to form in drops, until in five minutes there 

 were about 20 c.c. of liquid hydrogen. Further liquefaction was 

 prevented by " the solidification of the air in the pipes of the 

 apparatus, closing the orifice of the hydrogen jet." It is thus 

 evident that air freezes at a temperature higher than that 

 at which hydrogen becomes a liquid. 



Liquid hydrogen, according to Professor Dewar, is colour- 

 less and clear, with a high refractive index and a density 

 evidently greater thau that ascribed to it by theory, namely, .10 

 to .12. Its boiling point had not then been determined, but that 

 it is excessively low was proved by immersing in the liquid 

 , hydrogen the closed end of a glass tube containing air. The 

 tube as far as it was immersed became filled with solid or frozen 

 air. A further experiment made by Professor Dewar in this 

 connection was the liquefaction of helium (a recently discovered 

 element) by placing in liquid hydrogen a sealed tube containing 

 this hitherto considered permanent gas 



This highly interesting and valuable paper goes on to state 

 that chlorine was liquefied by Faraday in 1823, that sixty years 

 afterwards, VVroblewski and Olszewski produced liquid air and 

 that now fifteen years later the two last of the gaseous elements 

 to baffle efforts at liquefaction had been obtained as static liquids. 



Professor Dewar concluded by saying that "with liquid 

 hydrogen as a cooling agent, a temperature could be reached 

 within 20' or 30 of the zero of absolute temperature, and its use 

 would open up an entirely new field of scientific enquiry. No- 

 body could predict the properties of matter near that zero." 



F.T.S. 



